Definition:

Opitz GBBB syndrome is a pleiotropic genetic disorder characterized by hypertelorism, hypospadias, and additional midline defects. This syndrome was originally described as two distinct entities, the BBB syndrome with cleft lip, palate and mental retardation, and the G-syndrome characterized by gastrointestinal anomalies. Subsequently, both syndromes were merged and reclassified as Opitz GBBB syndrome. There are two forms of Opitz GBBB syndrome, which are distinguished by their genetic causes and patterns of inheritance. The X-linked form is caused by a mutation in the gene MID1 that encodes an ubiquitin ligase that targets phosphatase 2A for degradation. Autosomal dominant form results from a deletion at chromosome 22q11.2.